Hi Helen, this is a suspiciously large scat volume for a fox, though the scat diameter looks OK, and also scats of wild foxes and dogs almost always have visible fur and some signs of their wild diet visible on the outside such as seeds, berries, insects, masses of fur, feathers, or bone chips, so to my eyes my first suspect for this scat would be a domesticated animal. Another thing with any fresh, dark-coloured scat like this, is to break it open with a twig just to check that it is not full of ground up plant material, because it was really an unusual scat from a herbivore, such as a swamp wallaby or even a pig.
Is there anything else to convince me this is from a fox?